The present invention relates to linear induction accelerators and, more particularly, to a method for improving voltage regulation in linear induction accelerators.
Linear induction accelerators are used in scientific research to produce high-current electron beams. In this use, it is normally a requirement that the beam be stable and focused. The ability to focus such a beam strongly depends on the constancy of the beam energy. Ripple and droop of the accelerator voltage pulses are the major causes of energy variation in electron beams produced by linear induction accelerators (LIAs), thus making focusing of the beam difficult. Voltage pulse ripple and droop are caused not only by imperfections in the pulsed-power source, but also by uneven beam loading and core magnetization current.
Conventionally, a compensation resistor is placed in parallel with the beam accelerating cavity of the LIA to attempt to minimize the effects of ripple and droop on the accelerator voltage. The value of the parallel resistance, relative to the beam impedance, determines the effectiveness of this method. However, precision applications, such as flash x-radiography, require resistance values much lower than the beam impedance. Unfortunately, this mismatch leads to very inefficient energy transfer between the pulsed-power system and the electron beam. Even with extensive resistive compensation, the pulsed-power system, the injector, and the magnetic section must be very carefully designed in order to achieve a beam energy variation of less than 1%.
The present invention solves these problems, and presents a solution in the form of a varistor. A metal oxide varistor exhibits extremely non-linear current-voltage behavior, allowing it to respond to non-uniformities in beam current.
It is therefore an object of the present invention to provide improved voltage regulation in linear induction accelerators.
It is another object of the present invention to provide an easily implemented regulation for an electron beam produced by a linear induction accelerator.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.